When you use the words “High-King of Ireland” one very prominent name always springs to mind first. Brian Boruma mac Cennetig, better known to us as Brian Boru, a true giant of Irish history. This figure, who dominated the life of the island for decades at the end of the 10th and beginning of the 11th century, was a warrior, first and foremost. From what the sources tell us, barely a year of his life went by when Brian was not fighting somebody, in some form.

Brian was born sometimes in the early 10th century – the exact year is not recorded but could possibly be as early as the 920’s (though this seems extreme, making him over 80 when he died). He was a son of Cennetig mac Lorcan, head of the Dal Cais sept and ruler of the Thudmumu Kingdom – Thomond – in North Munster, based primarily around what is today County Clare. Brian’s famous surname, applied posthumously, may have come from the Beal Boruma fort, just outside Killaloe, which the Dalcassians held.

Munster was, at the time, a complex web of Kingdoms and dynasties, Gaelic and Norse, competing for total domination of the province. These wars and rivalries did not stop conflicts with those outside Munster, and areas in Mide and Leinster were often the focus of raids and assaults. The Dal Cais, their territory located north of the Shannon estuary, made good use of Ireland’s primary waterways for this purpose, with both Brian’s father and his older brother leading raiding parties up the river in search of cattle and plunder. In this, the Dal Cais could well have been influenced by the Vikings, their settlement of Limerick located so close, in terms of both tactics and naval technology – the Norse longboat and its shallow drafts well suited to this type of attack. Brian, as he grew older, would undoubtedly have taken part in such attacks, and his later use of the naval option in nearly all his subsequent wars can find its origin in this period.

Cennetig was succeeded by his son Mathgamain (another older son may have ruled for a short time in-between) in the 950s. The Eoganachta family were the nominal power in Munster at the time, but had been severely weakened by attacks from the Vikings, from the Ui Neills and from inter-family squabbling and assassinations. The Dalcassians, despite the small size of their holdings, had become a true military power on the rise, and Mathgamain simply kept this trend going during his own, quite notable, reign. Presumably, Brian was at his side throughout his campaigns in Munster, and in 964 they seized the Eoganachta capital at Cashal, a great military (and symbolic) blow to their foes.

The Dal Cais could thus claim the Kingship of Munster, but Mathgamain spent the rest of his life fighting to retain that title, his primary foes being Mael Muad mac Bran, an Eoganachta claimant, and Ivar of Limerick, the ruler of the local Norse power.

The Dal Cais military strength at this time is probably best seen in their victory at the Battle of Sulcoit, Tipperary, in 967, over the forces of Ivar. This defeat was decisive enough to allow Mathgamain, possibly with the assistance of Brian, to go on and plunder Limerick, a not inconsiderable defensive position.

The Norse were not done by any stretch of the imagination however. Ivar comes across as quite a villain in the (not entirely trustworthy) sources, a brutal tyrant of Limerick, and the constant threat from him may explain why the traditional enmity between the Dal Cais and the Eoganachta was set aside in favour of allying against him. This union led to Limerick being plundered again in 972, crippling Norse power in the region for a time, though Ivar was not yet totally beaten. After this, Mathgamain and Mael Muad resumed their fighting against each other for the rest of Munster. Brian must have been getting a taste for the complicated and dangerous game that was the making and breaking of alliances at this time.

In 976, disaster stuck the Dalcassians, as Mathgamain was captured by Donnuban mac Cathail, a leader of the Ui Fidgenti dynasty in north Munster. A strong ally of Mael Muad (and Ivar), he promptly handed Mathgaiman over and the Dal Cais leader was killed.

Brian assumed his brothers position without dispute. However old he really was, he was well experienced in battle by this point and was determined to expand his holdings. His eyes went far beyond Munster, and in order to fulfill those ambitions, he embarked on a brutal conquest of his local enemies.

Ivar and the Limerick Norse fell first. A vicious campaign in 977 and 978 resulted in their total defeat, a mixture of raids, set battles and attacks on Limerick itself, in which Ivar, his sons and possibly Donnuban as well were killed. A fight on Scattery Island, Clare may have been the pivotal engagement where Ivar and his sons were surprised and killed, presumably with a strong naval element helping Brian pull this off. The Norse power in Limerick, which had once rivaled that of Dublin was utterly smashed and the Dal Cais position in Munster was cemented. Some Norse remained, at Brian’s discretion, retaining the trade power and fleet strength that Limerick represented. In 978, he challenged and defeated Mael Muad at the Battle of Belack Lechta, location unknown. As with the Vikings, the victory was near total: Mael Muad was killed, his forces scattered or destroyed. Brian and the Dal Cais were now the overlords of Munster. That Brian managed to end what had been such a long struggle so quickly after his assuming of power is testament to his military skills.

Having pacified his enemies in Munster, Brian looked abroad again to Leinster and Mide, the lands he must have raided with his father and brothers in his earlier years. In this, he came into conflict with Mael Sechnaill, King of Mide and nominal High-King of Ireland, the man who had routed the Dublin Norse in 980. That first war between Brian and Sechniall was long and bloody, over 15 years in length, fought throughout Mide, Leinster, Munster and even holdings that both men held in Connacht.

Both sides led raids and invasions of the others territory. Both sides suffered setbacks, both sides lost battles. Brian became a master of combined operations in this war, successfully utilising both his land and naval forces together as the fight went on, using his fleet arm to distract and harry his enemies rear while making the decisive blow with his land forces, a strategy that allowed him to gain control and hold greater amounts of land in Leinster as time went on. Mael Sechnaill was no easy opponent, but he could never match Brian’s use of the waves, be it the sea or the rivers. In this, Brian’s use of his new Norse subjects, and their boats, may have been crucial.

By 997, Mael Sechnaill had had enough. He made a formal truce with Brian, recognising the latter’s control over Munster and southern half of Leinster, with Brian doing the same for Mael Sechnaill’s control over the rest of the country (and his title of High-King). They exchanged hostages, and began allying in efforts against Dublin.

Peace lasted only a short time. Sechnaill’s Leinster subjects, unhappy with his arrangement, rebelled. They placed Mael Morda mac Murchada, a prominent Kildare noble, on Sechnaill’s throne, nominally at least. He soon allied himself with Norse Dublin, under his kinsman Sigtrygg Silkbeard, a major Norse figure of the day.

Brian and Sechnaill combined their forces to combat the rebellion. Morda and Sigtrygg, unwilling to endure a siege of Dublin, marched out to meet them. Brian and Sechnaill clashed with the rebels at the Battle of Glenmama in Wicklow in late 999. Trapping the rebel army in a frozen valley pass, the resulting fight was large scale and bloody, for the times anyway. Morda and Sigtrygg’s forces were decisively beaten: a huge number of Hiberno-Norse were slaughtered, the rest scattering in three directions from the onslaught of Brian and Sechnaill. All sources indicate the battle was a huge and blood-drenched affair, with thousands dead. Brian had won a battle in extremely difficult conditions, thanks to his superior outmanoeuvring of the enemy force.

Brian moved quickly after Glenmama, conquering and occupying Dublin. Sigtrygg fled north, seeking support from Ulster nobles, support that never came. He soon returned, bending the knee to Brian, who re-instated him as Dublin’s ruler and cemented their new association with a double marriage alliance. Morda seems to have been similarly pardoned for his rebellion. Brian, with grander ambitions them holding Munster and south Leinster, recognised that slaughtering his enemies was not always the course to take, especially if they could prove useful in the future.

With the newly won support of Dublin, Brian enacted his plans for further conquest, launching an assault on Mael Sechnaill’s home province of Mide that same year, the first of the new millennium.

The actual events of this two year struggle are largely unknown. Mael Sechnaill had support from the King of Connacht and built bridges over the Shannon to facilitate this. But it availed him, or Connacht, not. In 1002, he surrendered his title of High King to Brian which included rule over Connacht. The legendary narrative states that, when challenged to battle by Brian, Sechniall could find no support from his nobles despite the observation of a month long truce from Brian. This story is, going by Brian’s nature, unlikely. However it fell out, Brian was now held the title of High King.

With Munster, Leinster, Mide and Connacht in his grasp, Brian looked northwards, seeking to become High King of all Ireland and not just in name only. Ten years of fighting with the Ulster Kingdoms and nobles followed, with Boru again making full use of his navy and army together. The Norse under Sigtrygg fought with Brian throughout, the Dublin ruler never forgetting how the Ulster nobles had refused to aid him previously, a hatred that ran deeper than his enmity for Brian. It was a long hard campaign, but Brian, with forces from most of Ireland at his call, prevailed, swamping the northern Kingdoms with numbers, and with pincer assaults from sea and land.

While all this was going on, Brian was securing the patronage of the major Christian settlement of Armagh, the source of the many Christian connections with Boru’s story. The Christian propaganda machine has always painted Boru in a good light, and around this time they begin to refer to him as the “Emperor of the Irish”. Whether Brian was as devout a Christian as he is often portrayed is beyond the scope of this project to comment on.

By 1012, Brian’s campaigns in Ulster were finished, and another total victory had been achieved. Brian was now the High King of Ireland in name and reality, having fought his way there with skill, ingenuity and bravery.

It was not to last. Mael Morda chaffed under Brian’s rule, and rebelled for a second time in 1012. With the assistance of some regional rulers from Ulster and his kinsman Sigtrygg again, he attacked into Mide, still ruled by Mael Sechniall, whom they beat in a battle near Swords. The King of Mide appealed to Brian for help, and the High King set out from Munster to assist him. Brian forced Morda’s forces out of Mide while his son Murchad attacked and ravaged south Leinster. The two armies then met up and besieged Dublin in late 1012. But, suffering from a lack of supplies and presumably poor weather, Brian was obliged to break off his blockade and return to Munster, a rare failure for him. Added to this was success that Sigtrygg’s fleet had over Brian off Cork, which appears to have neutralised much of his naval advantage.

Despite their success in holding out against Brian’s forces, Morda and Sigtrygg were in a bad spot. Ulster and Connacht did not come rushing to Brian’s aid, but, for the most part, they did the same for Morda and Sigtrygg, opting to stay out of the fight. Lacking allies and men, Sigtrygg departed Dublin in search of foreign support while Morda prepared at home for the renewal of Brian’s offensive. This uneasy peace lasted over a year, as both sides got ready for the inevitable battle.

Sigtrygg found his men in the Isles of Man and Orkney, Norse who opted to fight for him in search of plunder and loot. This is an important point, emphasised to counter-act much of the traditional narrative that surrounds the fighting that followed: the Norse fighting on Morda’s side were not seeking land in Ireland, let alone to conquer the entire island. Brian, in the form of Hiberno-Gaels from Limerick, Cork and Waterford, had plenty of similar people on his side.

Along with them, his traditional support from Munster and south Connacht, and a number of foreign mercenaries, Brian also had the help of Sechniall and his Mide army. He probably outnumbered Morda at this point, to the extent that he detached part of his force under his son Donnchad to again assault South Leinster, seeking to distract and break up the opposing force. But then some manner of disagreement between himself and Mael Sechniall resulted in the King of Mide withdrawing his forces, leaving Brian facing into an imminent battle, unmanned and in a bad position. He may still have outnumbered his enemy, but they were certainly better equipped and supplied, Brian having marched his army far beyond his reliable home bases. 7’000 or so on Brian’s side may have met 6’000 on the other.

The clash came at Clontarf, near the coast, north of Dublin. It was Good Friday, 23 April 1014.

Sigtrygg held a reserve of a thousand men in city, leaving his men in the battle to be commanded by his son. They held the left. The foreign Norse pitched their flags in the centre and right (near the beach) of their line, while Morda’s men choose to fight near their Dublin allies and the centre.

Opposing them, Brian had his foreign mercenaries on his right, with his Munster and Connacht contingents with him in the middle. His Dalcassian brethren held the left while Mael Sechniall’s forces apparently observed the fighting from a distance.

The two armies edged close to each other in the traditional shieldwall pattern, finally engaging sometime in the early morning. The Vikings on both sides had the better of it, pushing back whoever they faced. On the Irish left, a vital blow was struck when the Norse leader Brodir apparently fled, leaving those forces leaderless against the Dalcassian soldiers, Brian’s most loyal and battle-hardened. By the afternoon, the Viking right was collapsing, the foreigners fleeing to their ships.

In the centre, things were more even, as Morda’s men and their Viking allies smashed into Brian and his Munster contingent. Again, a Norse leader, Sigurd, fell with disastrous consequences. The fighting was long and tiring, several pauses were observed by both side, but as the day wore on, Brian’s centre was still holding.

On the other flank, things were clearly going Brian’s way, his own foreigners advancing.

With their flanks collapsing and many of the Vikings already trying desperately to retreat to their ships, a rout ensued. The Dalcassians had taken the beaches, preventing retreat there, resulting in many drownings; the rebels and the Vikings attempted to flee back to the safety of Dublin only for Mael Sechniall to finally step in, preventing this avenue of escape. A slaughter of the remaining rebel/Viking forces followed. Morda was killed, joining Brian’s son Murchad and the Norse leaders.

However it happened – during the battle, or after at the hands of a fleeing Brodir while Boru was praying – Brian also did not survive the day, cut down in some fashion. He must have been ancient for the time, but it does add to the romance and “epicness” of the fight that in the moment of arguably his greatest triumph, Brian himself was brought low and killed, dying by the sword having lived by it for so long.

The Battle of Clontarf has taken on a much different nature then its reality but it was not a decisive end to the Vikings in Ireland, and was not the final stroke in a liberation of the island from Norse rule. It was the final battle of what was essentially an Irish civil war, with Norse mercenaries taking part on both sides.

Mael Sechniall regained the High Kingship after the battle, though the country that Brian had built soon collapsed into the typical inter-Kingdom/factional fighting and warring that defined the previous centuries. Sigtrygg lived and reigned with varying fortunes for another 30 years.

Warfare at the time remained as it had been – focused on infantry, the shield wall, the cattle raid. Brian is a very rare thing: an Irish leader who made great benefit from the naval dimension. It was his great advantage, mastery of the waterways and he used his knowledge to its fullest extent. It was vital in his victories over Mael Sechniall and the north. No other Irish leader, before or since, can say that they used the waterways of Ireland to the same extent. Brian took the advantages that the Vikings haD brought to Ireland and used them for his own purposes. He took provinces like Munster, Leinster and Connacht and was able to get their men to fight for him.

He was also a master of knowing when to strike, when to barter and when to ally. His uniting of the country shows extraordinary perseverance and military know-how, as it seems only his failure to take Dublin in 1012 marks his otherwise unblemished war record. His success speaks for itself.

And with the arrival of the Normans to come, Brian’s life marks the last real “great” time of free Ireland, its own Kings, wars, dynasties’ and rivalries, before the arrival of the English foe who would define Ireland’s military history for the next millennium. Brian is looked at, perhaps, as the last example of a really powerful Irish champion, a giant who united the country.

That was still to come. The military history of Ireland contains enough to note the period between Boru’s death and the Norman arrival as unique enough, and it is that period – and two sieges of the same city in particular – that will be the focus of the next entry.

To read the rest of the entries in this series, click here to go to the index.